A number of chemical agents have heretofore been used for controlling plant diseases. However, the problem that plant pathogens have acquired resistance to the chemical agents becomes remarkable due to frequent use or excessive application, etc., of the chemical agents having similar structures and same functions for controlling the same kinds of diseases.
On the other hand, consumers' needs for agricultural chemical-reduced crops and social needs to reduce environmental loads due to agricultural chemicals have now increased.
Also, in a farmer's field where the chemicals have been actually used, when two or more kinds of chemicals are used in admixture for the treatment by the tank mix method, there are many risks to lower the effect of the other chemical to be mixed with each other or possibilities to cause chemical damages against plant materials depending on a combination of chemicals where they are not well-suited to each other.
Under such a situation, it has been desired to develop a plant disease control composition having high effects against fungi or bacteria which are resistant to existing chemicals, and having high effects with a low amount of an effective ingredient. Moreover, for the purpose of preventing plant pathogens from obtaining resistance, it has also been desired to develop a plant disease control composition comprising components (compounds) having different basic structures and different functions with well-suited to each other, and a method for controlling plant diseases.
It has been known that a quinoline compound represented by the formula (I) shows, as a fungicide, controlling effects to rice blast (Pyricularia oryzae) and gray mold (Botrytis cinerea) of tomato, cucumber and kidney bean, etc., by an application method such as seed disinfection, foliar spray treatment, etc. (Patent Literatures 1 to 4).
However, it has never been known yet about a controlling effect of the quinoline compound represented by the formula (I) and the other fungicide(s) in admixture.    [Patent Literature 1] WO 2005/070917A    [Patent Literature 2] JP 2007-1944A    [Patent Literature 3] WO 2007/011022A    [Patent Literature 4] JP 2007-217353A